Discussion in 'The Workshop' started by noweyout, Jun 22, 2009.
My wheels are Mavic 823 UST
Since you have a slow leak just use Stans- it will seal the valve stem leak no problem.
Another ~50grams of sealant won't kill you, especially since you're already rolling on 823s.
Get a new oring for your valve, clean the hole well, install the valve with a bit of silicone Dieeletric grease that can be had at any local auto parts house. Yes the stuff for sparks plugs,its the same stuff for caliper pins, for inuslating ele connections, pretreating oring for install....... works great
I don't think a new o-ring will help in this case. Actually, in the case of the EX823 rim, the o-ring does not provide any type of air sealing function. The outside rim wall is not air tight at all. My thoughts are that the o-ring just prevents the valve stem locknut from loosening up and allowing the inside seal to leak. The valve stems seals at the inside rubber base.
OP stated that the air was coming out at all the nipple holes. The o-ring is on the outside of the rim. The leak is somewhere on the inside wall of the rim. Either the valve base is worn or a cracked inside rim wall.
Pato is right, from what I remember there is a semi-circle gasket that fits the profile of the rim built into the valve stem. I may be mistaken but if he is using the Stan's valve stems the issues is likely incompatibility due to the "universal" fit of the inferior part. I still maintain trying to seal the base is the best course, spreading the gasket material where the leak is most likely located rather than dumping in volumes of goo that will eventually harden leaving lumpy deposits within the rims internal cavities throwing things out of balance.
A side note for the weight weenies the amount of that slop it takes to perform adequately is not only heavier but much tougher to seal than a lightweight tube on the trail after being sent over the bars due to burping a bead or slashing an un reenforced not designed to hold air. So many injuries and DNF's from that shit and still droves believe the hype rather than dropping a few more bucks on a proper UST set-up.:?:
O-rings seems fine, just a little cracking. But I bought a whole box from hardware store just incase. I seriously think it's the valve stem not sealing properly so I'll try the grease first before I go to stan's. I really don't want to use it because I know it can get messy and I know I'll leave it in there for a while (6m to 1yr), I'm afraid it'll dry out and dry other things out also.
I am thinking about getting a lighter wheelset so maybe here is my chance. I ran some numbers and if I go back to a tube/tire setup on 1900g wheels, it'll still be 3 lbs lighter than what I have now. But I'm running my options right now.
Again, before you go and try to put a band-aid on a problem I'd swap valve stem from the good wheel first to see if it is indeed the root of your problem.
Is the current valve stem an authentic Mavic unit designed specifically for their rims or are you using the Stan's generic unit? The Mavic unit has a square base that is designed to fit in the center channel of the rim. The Stan's design is round and may overlap onto the side creating a pocket at the corners allowing air to leak out.
If it is an authentic Mavic unit and it still leaks after swapping it out for a known good valve, I'd try to use pliers to tighten the locknut 1/2 turn past finger tight to creat a tighter seal at the base. If these steps don't fix the problem then I'd really advise you to look for tiny cracks on the inner rim wall or weld.
Where in the SGV are you located? I'm in Downey and can help you diagnose/fix the issue if you want to swing on by.
Thanks for the help. It is a Stan's valve stem and yes the base is rounded. I did see it as a problem at first but it held air really well for a while so I thought nothing of it. The air seems to be leaking out of both wheels. When I get home, I'll make sure to check the seal on the valve stem and tighten it more if needed. I'm in Alhambra but starting to ride turnbull often. If its still not fixed I'll shoot you a PM.
My wheelset weighs 2500g and my UST tires weigh 800g each. Its over 9 lbs right now. I can get it down to six with the right wheels w/ Kenda SB8's.
Weight is relative, look at the small number (45-58) to determine the actual width of the tire and or tread as the inch measurements are generally worthless. Currently I roll the WTB Mexi-wolf 2.1 (640gms) which is closer to a 2.3 due to the 52cm casing, paired with 68 gram flyweight tubes they roll fast on climbs and are very predictable on the way down. SB 8's work better as a rear and lousy on anything but hardpack but enough thread domination I have work to do.
I think that's your problem right there. Give the 1/2 turn with the pliers a shot. If not, bring both your wheels by. I've got spare Mavic valve stems you can try out.
Dropping 600g is only 1.3 pounds. Tubeless tires are a bit heavier, but then you don't have the added weight of tubes. Wow...your rims are HEAVY!!!!
Well yeah, I have lots of time to kill so...
SB8's are 500g x 2 + 99g light tubes x 2 + 1900g = 3098 g = 6.8 lbs
Current Nev are 800 g x 2 + 2500 g = 4100 g = 9.0 lbs
So I need to make a correction. 2.2 lbs.
My bike = 29.8 lbs so 27.6 lbs would be nice.
Exactly. O-ring doesn't seal in air. Take Pato up on his generous offer of mavic stems.
Ga... Yeah Pato is right, I am thinking of a differnt style valve. But still, the silicon Dieeletric grease...thin layer..... on the sealing area.
Pump them up...!!!:lol:
I was on Amazon looking for Mavic Valves and they are about $15 each. I'm going to the LBS tomorrow but is that how much they run usually?
online about 13 to 13.50. ~~~~ LBS 15 to 16
I have a couple of slightly used ones you can have for $15.
$3.00 for a tube, which comes with a stem... or $15 for a Mavic stem, plus Stan's, plus burps, plus tires blowing off the rim and spraying spooge everywhere in the garage. :?:. I can see the benefits.
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